In order to make spectacles properly fit a wearer, the frame of each pair of spectacles must typically be individually adjusted by a dispensing optician. Such adjustment for proper fitting is typically required for new spectacles, and may also be required subsequently, if the spectacles goes out of shape.
Spectacles having a plastic frame, which plastic is typically acetate, are properly heated to a temperature of about 250.degree. F. to about 350.degree. F. in order to bend the frame for adjustment purposes. Failure to sufficiently heat the frame may result in the frame snapping during the adjustment process. Excess heating may cause the frame to excessively distort, may damage the spectacle lenses, particularly if plastic lenses, or may damage the finish of the spectacle frame or lenses. Accordingly, proper heating of a plastic spectacle frame is a delicate operation that must be accurately controlled.
One method of heating a plastic spectacle frame is to use hot air from a controlled temperature hot air blower. This method is unpopular for a variety of reasons, including the high cost of the specialized equipment and the risk of a person using the equipment, such as an optician, exposing his hands to the hot air. Further, this method does not readily allow for specific parts of a plastic spectacle frame to be targeted for localized heating.
Another method of heating a plastic spectacle frame includes the use of a frame warmer that retains an amount of solid granular material, such as glass beads. The glass beads are heated in the heating pan, commonly known as a salt pan, to a temperature of between about 250.degree. F. and 350.degree. F., which temperature is sufficient to make the plastic material of the plastic spectacle frame temporarily slightly pliable without actually melting the plastic material. In this manner, the plastic spectacle frame is pliable enough to be bent slightly to adjust the shape of the spectacle frame properly to a wearer's head. Once the spectacle frame has cooled, the frame retain this newly adjusted shape.
On occasion it is necessary to bend an spectacle frame only at the bridge area thereof in order to allow for relative angular adjustment of the lens portion of the spectacle frame. On such occasion, it is highly desirable that no other part of the spectacle frame be bent. In order to bend the plastic frame only at the bridge area thereof, it is necessary that the heating of the plastic frame be localized at the bridge area so as to preclude the chance of any other part of the spectacle frame from becoming warm and pliable, and thus easily bent. Such localized heating cannot be readily accomplished with either of the two common prior art methods of heating a plastic spectacle frame, as discussed above.